Auto merge of #53599 - matthiaskrgr:split_str__to__split_char, r=frewsxcv

use char pattern for single-character splits: a.split("x") -> a.split('x')

src/libcore/str/mod.rs

@@ -59,7 +59,7 @@ pub mod lossy;
 ///
 ///     fn from_str(s: &str) -> Result<Self, Self::Err> {
 ///         let coords: Vec<&str> = s.trim_matches(|p| p == '(' || p == ')' )
-///                                  .split(",")
+///                                  .split(',')
 ///                                  .collect();
 ///
 ///         let x_fromstr = coords[0].parse::<i32>()?;

src/librustc_incremental/assert_module_sources.rs

@@ -89,7 +89,7 @@ impl<'a, 'tcx> AssertModuleSource<'a, 'tcx> {
             (&user_path[..], None)
         };
 
-        let mut cgu_path_components = user_path.split("-").collect::<Vec<_>>();
+        let mut cgu_path_components = user_path.split('-').collect::<Vec<_>>();
 
         // Remove the crate name
         assert_eq!(cgu_path_components.remove(0), crate_name);

src/librustdoc/theme.rs

@@ -205,7 +205,7 @@ fn build_rule(v: &[u8], positions: &[usize]) -> String {
              .replace("\t", " ")
              .replace("{", "")
              .replace("}", "")
-             .split(" ")
+             .split(' ')
              .filter(|s| s.len() > 0)
              .collect::<Vec<&str>>()
              .join(" ")